1. Field of the Invention
The present invention relates to a contact pin arranged to a socket for an electrical part for detachably holding an electrical part such as semiconductor device so as to be electrically connected to the electrical part and also relates to a socket for electrical part provided with such contact pin.
2. Related Art
In prior art, there is known an IC socket, as a “socket for an electrical part”, for detachably holding an IC package as “electrical part”.
Such IC package includes BGA (Ball Grid Array) type or LGA (Land Grid Array) type, in which a number of terminals are arranged to a lower surface of an IC package body having rectangular shape.
On the other hand, the IC socket has a socket body to which a number of contact pins of surface-press-contact type structure are arranged, through which a printed circuit board and the IC package terminals are electrically connected.
The contact pin has a tubular portion, in which a lower contacting section press-contacted to the printed circuit board is accommodated in a lower portion of the tubular portion to be vertically movable and an upper contacting section press-contacted to the terminal of the IC package is also accommodated in an upper portion of the tubular portion to be vertically movable. A spring is further accommodated in the tubular portion to a position between the lower and upper contacting sections so as to urge these contacting sections in opposing directions.
In a state that the IC socket is secured onto the printed circuit board, the lower contacting section of the contact pin is urged by the spring to thereby press-contact the printed circuit board. From this state, the IC package is mounted and accommodated on the socket body and is then pressed from the upper side thereof. Thus, the spring is compressed and, according to the urging force of this spring, the upper contacting section is press-contacted to the terminal of the IC package at a predetermined pressure.
The contact pin of the conventional structure mentioned above is, however, composed of many (four) portions of the tubular portion, the lower contacting section, the upper contacting section and the spring, so that assembling process is increased, and moreover, it is troublesome to manufacture the tubular portion having a hollow structure, involving much cost, thus being inconvenient.
In addition, in the conventional structure, a number of such contact pins are arranged in conformity with the arrangement of the terminals of the IC package, and in a case if the arrangement of the contact pins differs from that of the terminals of the IC package to be inspected, it is required to be changed with another IC socket having an arrangement of contact pins corresponding to the arrangement of the IC package terminal, thus being also inconvenient.